Loud-speaker unit



Oct 25 1927' L. H. FRONK LOUD SPEAKER UNIT Ott. 25. 1927.

.L. FRONK' LOUD SPEAKER NIT Filed April 23. 1926 sheets-sheet z Invento l/eer/ Won/f @075 .in :bothmagnetic poles, of the coil and the permanent `magnet in order to produce an Patented Oct. 25, 1927.

PAT

ENT ori-fic:Ei

` LESTER H. lJFIEtOlYl'K, OF SALT LAKE CITY, UTAH. Y

LOUD-SPEAKER UNIT.

l Application led April 23,

objectvoi' the inventionis to provide aspecial construction for the loud speaker unit in which aspecially shaped permanent magnet is usedwith independent pole pieces forminga housing for an electric coil and an e armature to `be Aoperated fthereby in which a substantially uniform luX iows at eiiicient operation of the armaturewhich is connected to aevsuitable diaphragm structure from whichthesound reproduction is obtained which has beenfound to be of a strong and mellowcharacter. l

A `further obj ect ofthe invention resides in the special construction of the coil mounting with the method of suspending the armature in the coil for `free oscillating movement in order to obtain eiiicient sound reproduction with weak currents, and which will prevent sound distortion when 'reproducing` sound with strong currents and considerable volume.` e

The invention `further comprehends the provision of aspecial diaphragm housing and mounting in order to properly center thediaphragm inits mounting Aand prevent it from being set too tight, off side, or in otherthan a very level position. The invention Vcomprehends numerous other objects residing in the details of construction and the relation of the parts to permit the ready and convenient assembly thereof in order to produce an assembled construction at a substantially rlow cost, which lare all point-ed out more particularly in detail in the lfollowing description and in the claims directed to a preferred form of construction, it being understood, however, that` various changes in thesilze,V shape and relation. of these parts may be made without departing from the spiritfandv scope of the invention as herein `set ortlrc l' In the drawings forming part pf this application :f-

Figure l isa"V plan view of the assembled figure unit. y v n.

Fig.A 2 is a side elevationther'eof. l*

Fig. 3 is a verticalsectiona'l view taken on um une 3 3 of Fig. `1. i

Fgfje is a vertical` sectional view taken en pagina; @i pf rig.1 1

V1926. Serial No. 104,080.

A Fig. 5l is an` enlarged horizontal sectional view. `taken on the line 5 5 of Fig. y4f. ,e F ig. 6 is a perspective of one of the pole Placesi f j Eig. 7 is a sectional view taken on :the line 7--7 of F ig. 5.

\ 1, indicates the-plate member and support for the assembled unit of annular form and having `an annular recessf formed in the .lower face thereof indicated at `2 from-the`- edge portion of which depends the annular flange' 3 adapted to seat within the annular recess 4 in the cap 5. The plate memberl is suitably secured to the cap.inemberf5` by screwsil or the like and isadaptfedto secure the .diaphragin in operative position in the recess .tot Ythe cap memberby engagement withthe washers 8 of ring shape which are superposed on the opposite facesof the ldiaphragm as clearlyshown inFig. 3. With thisyconstruction the diaphragm j? is respectively centered in the recess 4 and held against movement by the plate member compressing jthewashers or packing rings 8 which are preferably offrubberv or similar material and; provide 1a rigid mounting for the edge portionyofthe diaphragm. f

i The packing ring placedbetweenithediaphragm-7v and :the 4cap member 5'is seated in an annular groove 9l in the recesslsothat it will be iirmlyretained in placefduring Vthe .operation of the. diaphragm. The cap member5 is'provided with a sleeve ,extension 10 threaded at the outer end to whichan amplifying horn may be attachedfor obtaining welhknown results in the art.A The. base plate member l is providedwith Aa plurality .of holes l1 4providing communicationwith thechamber or recess 2 formedin the ,lower face'foi thefplate member tok permit free pasf sage oi. air into the chamber so that the air that Aisset in motion by the vibrationof the diaphragm Vmay be equ'alized, and thereby more eficientlyl and lpyc-:rfectly reproduce sound Aby the operation `ofthediaphragm Without distortion. .l A diaphragm pin-.12 connects thegdiaphragm 7 Withthe armature lwhich-isof substantially -rectangularorm as shown in Fig; 5.v The/diaphragmpin 12 is connected vto one end of this rectangular armature while the `central portion Ithereof isfprovided with .a `suitable Wire pivot mounting between@ pair otclampmembers 15.. This1 wire let is remettant 'ai tight in fc-ae` eeaaf'aigperteaes ne Y shown at 16 in Fig. 7, While the end portions 4extend thru Aopenings in the armature to the opposite face and then along the opposite face of the armature tor connection to the clamp members 15.

This Wire is suitably solderedA to the arma-l ture in its length of contact therewith, `and extends through openings in the centraloflset portion of the clamp members as clearly shown in Fig. 5, having the free ends eX- Vtended laterally and suitably soldered or serve to retain the end supporting plates 18 in rigid engagement With ,the lateral ends of theclampimembers so that a complete coil supporting form is provided for the coil 19. A ysuitable insulating covering is preferably Wrapped around. the plates 20 and the clamp membersl on which the coil 19 is Wound while the completed coil is covered with a suitableV insulating and protecting covering 22 as more partifcularly shown in Figs. 5 and-7. The --diaphragm pin, armature, clamp members, vplates 20,-Y and end plates 18 for supporting the coil 19, are all preferably formed of nonniagnetic metal such as glass, copper, or the like'ihaving the desired qualities for the purposes for `which it is used'. IThe armature 13 is preferably formed of silicon steel.

Thecompleted coi-l structure and armature as above"'described are received and housed apair ofpole pieces 23 and 24 respective- Vvly, ivhich form lower and upper pole pieces respectively and are ot duplicate construction asfclearly illustrated in Fig. 6. These pole pieces include plate portions 25 from thel opposite'sides ofivliich are `laterally eX- vtending-langes 26 arranged in spaced parallel relation and having projections 27 from .the centralv portions oftheir'ends yas clearly vs hov'vn in Fig. 6. These pole pieces are Imoruited in-opposed relation in the assembled positionof the-parts as shown in Figs. 2.and 4 and have their transverse centers co.-

iniident with; the central longitudinal plane of'th'elarinature;,13, asillustrated in Fig. v2. rejections 27 from ythe end of' the lateralilianges 26 extend into close proximity fea/Ch other 'and in close ybut spaced parallel v'relation Withjopposite Vsides of the armature 13 as may be clearly ascertained in Figs.' 2 "and 4. VThe en d,support-incr vplates reanath@y assembiedoii 19 'as aove debase plate 1,v the cap member 5, theA .flespect to the armature.

- the pole piece 2 3.y

scribed are received between the flanges 26 and entirely Ahoused thereby as shown in Fig. 2, the base portions 25 engaging the opposite edges of the end plates 18 and rigidly mounting the coil assembly in position between these pole pieces.

-Theends of the pole pieces are formed with openings 28 Which slidably fit over the posts 29V mounted on the base plate 1 and rigidly secured in assembled position by means ot nuts 30 threaded on these posts 29. This pole piece structure, it will be seen, prof vides a rigid assembly and mounting of the coil `and its supporting structure together ivith the armature supported in the coil sup porting structure so that a simple and efficient mounting is provided Vfor these parts.

"A permanent magnet- 31 of special design is employed with this loudspeaker unit construction which is formed with an arcuate portion r32 of substantially semi-cylindrical shape terminating at oneside in the straight end 33 Which is tangential to the end ofthe semi-cylindrical portion 31 AWhile the opposite end or' the semicylindrical portion merges into the straight portion 3ft, parallel with .the end 33, and Which terminates in thev laterally extendingv end 35. The end 35 extends toivard end 33 and substantially at right angles thereto and offsetrelative to the the end thereof as can be clearly ascertained transverse plane of the end 33 and beyond by an examination of Figui.

1 The central portion ofthe end -35 of the permanent magnet is formed with a V- shapedrecess 36 to provide a passage for the diaphragm pin 12, as-clearly shown in Figs. L and 5. The permanent magnet .is

mounted on the base plate 1 with the end 35 in Contact therewith having the end portion thereof positioned in contact with the lower pole piece 23 and centered `so that the cen- 'tral portion oi the magnet is centered with In this position ot the magnet, the end 33 will overlap the pole piece l2%1 and have the inside'surface vof the endV portion contacting with said polel piece 24 at the opposite Vside from the point of engagement of the end of the portion 35HWith securing bar v37 of suitable non-magnetic metal is positioned transversely across the end portion 3 5 of the permanent magnet 31 and secured Vat its endtosuit'able posts 38 mounted in thebase plate 1 by the nuts' 39 threaded thereon. This 'form ot mounting provides an etlicient clamp to p ermit the ready attachment and v adjustment .of the pole piece ivithV respect to the armature and coll mounting structure yas Well as the pole pieces'23 and 2,4. g One of the flanges' 26 'on' each of ,the pole pieces 23 and 2 4 and the flange positioned adjacent to the diaphragm pin 12 is formed with a groove 40 in the central portion to v ment of the diaphragm pin, while the central portion of the plate member 1 is provided with a central opening 41, through which the diaphragm pin passes and operates.

lVith the above described construction, it

will be understood that the suspending structure for the diaphragm 13 as clearly illustrated in Figs. 5 and 7 provides a ten# sion on the diaphragm 13 and the pin and diaphragm 7 of such a character that it will not be subject to rattles or other looseness while the magnetic flux of the permanent magnet 31 will have a complete circuit through the pole pieces andl will be concentrated at the gaps between these pole pieces at the ends of the projections 27 where this `field will exert its maximum force on the armature 13 at the opposite ends thereof.

In being properly centered between the flanges 26 of these pole pieces, it will be seen that the action of both the south and northern poles of the permanent magnet will equalize at the gaps between the pole pieces and exert a substantially even and equal pole on the armature. This equalized magnetic flux of both north and `south. polaritylo'per-v ating and at equal distances Vfrom the pivotal mounting of the armature provides for the easy and eflicient operation of the armature through variations of this flux which occur upon the energization of the coil 19. By positioning the coil between these pole pieces in the manner illustrated and described above, it will be seen that the' north` -and south magnetic poles of the coil will occur at-the flanges 26 of the pole pieces so that the flow of magnetic flux across the `gaps between the ends of the pole pieces 23 and 24 will directly operate the y armature. In this way, substantially weakV currents flowing in the coil 19'will cause a fluctuation in the flux operating the armature` and thereby produce the reproduction of the feeble currents in sound waves which have been found in the practical operation of the device constructed as shown in the drawings to produce a substantialvolume of 4sound for these weak currents.

This result is obtained through this balanced action of the magnetic fields on the. opposite ends ofv the armatures and on opposite polarity and through the relation ofthe pole pieces to ends of the coil 19.

The variation of the flux of opposite po-V the l extension to directly operate the diaphragm or arma.a ture. This equalization of the flux of the permanent magnet on the opposite ends of the armature together with the poleof the coil being at the flanges 260i vthe pole pieces for directly varying the field acting on the i armature is lfound to result in a more perfect reproduction of the entire audlble range of sound waves, with substantially no dis-l tortion and'through the balancing action to eliminatek mechanical vibrations from transmission and reproduction by the diaphragm.

'set forthform the novel features of this in- Avention.

Having thus described my invention, what I claim as new is l 1. An armature mounting for" loud speaker units, comprising a support, a pair of clamping members secured in 'spaced parallel relation to lsaid support, an armature positioned between' Vsaid clamp members, and a wireinember' rigidly secured to. said armature in its central portion and having the terminal thereof rigidlysecured to said clamp members. v

2. An armature suspension and coil support, comprising a supporting means, aV pair of end plates mounted in said spaced parallel relation insaid supporting means, a pair of clamp members mounted in spaced parallel relationinl opening said end plates, a pair of plat-e members mounted on opposite sides of said clamp members and positioned members forming an armature housing with said clamp members, an armature suspended in thearmature housing between said clamp members, and a vcoil mounted on theplate members and clamp members around4 said armature housing and between said Vend plates. i

A permanent magnet for loud speaker units comprising an Velongated flat bar member, formed with a semi-cylindrical portion, the end portions extending in parallel relation from said semi-cylindrical portion and terminating in unequal lengths, the longer having the terminal thereof formed with a lateral extension terminating in substantially the centralv plane between said extensions. Y Y

In testimony whereof l aiiix my signature.

1 LESTERH. FRONK. V 

